Published: June 22, 2008 02:23 pm            

John Watson: Renewable natural gas plant to open in Dublin

On June 11 Environmental Power Corporation, a leader in the renewable bioenergy industry, held groundbreaking ceremonies at Dublin to mark the beginning of construction on its Rio Leche Estate renewable natural gas facility. The facility, owned and operated by Environmental Power’s subsidiary, Microgy Inc., will generate pipeline grade RNG from dairy cow manure and other waste products.

The Rio Leche facility is expected to generate 635,000 MMBtu of RNG per year, the energy equivalent of 4.5 million gallons of oil. The facility will use a thermophilic, co-digestion, anaerobic digestion process to generate methane-rich biogas, condition the gas to natural gas pipeline standards, and transport the RNG to market by the Enterprise natural gas pipeline system.

In addition to generating a reliable source of RNG, Rio Leche is expected to help local dairies manage their waste. The facility will help reduce odors, protect groundwater, and help farmers to operate within nutrient management guidelines.

Microgy Inc. operates a facility northwest of Stephenville, the Huckabay plant, which I toured Wednesday. Mark Hall, senior vice president, gave me a guided tour.

The site used to be a composting site for cow manure collected from the many dairies in Erath County, some of which contain herds of a thousand cows or more. Runoff from these dairies was polluting the Bosque and Paluxy Rivers.

To cut down on the water pollution, the manure from the dairies was trucked to the location northwest of Stephenville and composted. The composted material was used by the Texas Department of Transportation along the roadsides with grass seed to help grass grow. Most of the leftover material from the digesters is still used for this purpose.

In open-air composting large quantities of methane gas are released into the atmosphere. Methane is one of the greenhouse gases responsible for global warming. Methane from animal waste has a global warming effect that is 21 times that of carbon dioxide.

Enter Environmental Power Corporation. They built eight large tanks, or digesters, that hold almost a million gallons each and started harvesting the methane gas from all this manure.

Open-air composting is aerobic, and what is being done here is anaerobic, that is, in the absence of oxygen.

The manure is dumped near the plant and, as needed, it is picked up with a front-end loader and dumped in a slurry pit. Water is added to create liquid slurry. A few thousand gallons of the slurry is pumped into the top of each of the eight digester tanks every day. An equal amount is removed from the bottom of the tank.

The slurry removed from the digesters is then transported to a separator where the liquid is separated from the solids. The liquid is returned to the slurry tank to be mixed with more manure. The solids are carried to the compost pile; ready to be used as is or aged a while longer.

The gas coming from the digesters is about 60 percent methane combined with other gasses and chemicals. The gas is cleaned to remove undesirable gasses. After the gas is cleaned it is pressurized and sent through a pipeline to enter the main natural gas distribution pipeline three miles away.

They do all co-digestion here, so that means they are not just converting the manure to biogas, but also taking food waste, grease-trap waste and the waste left after producing bio-diesel from soy beans. The grease-trap waste used here comes out of the Dallas/Ft Worth area.

The plant will make enough natural gas to heat 11,000 homes.

At this time 120 operate digesters in the United States, according to the Environmental Protection Agency, but more than 3,700 projects operate in Germany and many more throughout Europe, where incentives have been offered for many years to produce biogas from anaerobic digesters.

“There is a lot of discussion about natural gas use in vehicles, and it has become a popular fuel for bus and corporate vehicle fleets,” said Hall. “I see natural gas vehicles in many large cities, and it is popular for use in ports and similar cargo transfer locations.” Natural gas burns cleaner and produces fewer pollutants than either gasoline or diesel.

Taking waste products, cow manure, food waste and grease trap waste, removing them from the environment so they cannot pollute the ground water, and collecting the methane gas from it rather than releasing it back into the atmosphere as a greenhouse gas, and producing a commercially viable product, natural gas, is a win-win situation all the way around.

Other plants are in the planning stages for Texas, with a groundbreaking scheduled for sometime in August for one near Hereford in the Panhandle.

We have all the Barnett Shale gas that scientists say took nature millions of years to produce from plant and animal waste from the age of the dinosaurs, but now, with modern technology, natural gas is produced from plant and animal waste in 21 days.



John Watson is a Cleburne resident who can be reached at texastraveler@sbcglobal.net.

        

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